[mutter/wip/fmuellner/fix-titlebar-constraint] constraints: Fix titlebars going off the bottom

[Florian Müllner <fmuellner src gnome org>]

commit a0909c34403d14cc17ffb86b9ce1b41fee12c7e5
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Jan 16 01:09:26 2019 +0100

    constraints: Fix titlebars going off the bottom
    
    The "current" rect includes the frame, so in order to keep the
    titlebar on screen, window movement must be restricted to at
    most (height - titlebar_height) past the work area bottom.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/391

 src/core/constraints.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/core/constraints.c b/src/core/constraints.c
index 078dbc063..f743bae5b 100644
--- a/src/core/constraints.c
+++ b/src/core/constraints.c
@@ -1594,7 +1594,7 @@ constrain_titlebar_visible (MetaWindow         *window,
       MetaFrameBorders borders;
       meta_frame_calc_borders (window->frame, &borders);
 
-      bottom_amount = info->current.height + borders.visible.bottom;
+      bottom_amount = info->current.height - borders.visible.top;
       vert_amount_onscreen = borders.visible.top;
     }
   else
@@ -1673,7 +1673,7 @@ constrain_partially_onscreen (MetaWindow         *window,
       MetaFrameBorders borders;
       meta_frame_calc_borders (window->frame, &borders);
 
-      bottom_amount = info->current.height + borders.visible.bottom;
+      bottom_amount = info->current.height - borders.visible.top;
       vert_amount_onscreen = borders.visible.top;
     }
   else